Sorry if this is not the brightest question but I have just started getting into mission design, mods, addons...etc. If I use a mod (@m107) in the mission editor and I want to use it in MP with my clan, does everyone who wants to join the server with that mission need to also have the mod added to their ArmA 3 folder? Sorry if this is off topic. The mod works fine for me in preview or MP internet, but no one in my clan can join the server with this mission. Prior to adding this mod, everyone could join the mission.

#MajorLeeStoned :
How do server keys work?Does it mean I can get into a server that is nor running the mod?Also where do I install the key?

It is something I forgot to mention, though its not a biggy. Just put a "keys" folder in your mods folder
in the same one as the "addons" folder, so it would be

@your_mod_folder_name\addons and then @your_mod_folder_name\keys

So as you see, in the "@your_mod_folder_name" folder you will now have the "addons" and "keys" folders together.
Then just drop the keys in that keys folder and your done.

Yes it is to let you use mods on a server which accepts or uses them same ones, IF the server does not allow mods
or has the same as yours ie the same version etc, then it will kick you off the server.

Hello! I try to install mod @DEditor:
1) Put folder with mod to D:\G\Steam\SteamApps\common\Arma 3
2) I add a Launch Parameter to Steam in Properties: -mod=@DEditor
3)In the game, in Options\ Expancions I see that mod, it present here.
BUT in the Editor, when I try to insert Unit there are only Blufor, Opfor, Independent, Civilian and Ambient life, NO Empty in the Side string. The game see the mod, but the Editor not see the mod, how it can be? (sorry for my english)

Struggling a bit with understanding how to install mods myself and also a ARMA3 noob........
Firstly managed to install the CBA and shackTac HUD mods not by linking them them in the steam properties start button but in game under the expansions menu I saw them and enabled them(simple)
1)Trouble is when I try install some of the weapons mods (mk14 and m4) this way they are not appearing in the expansions menu in game - so I try and start them under the steam properties start menu (drop in the mod text as above) - they now appear in the expansions menu in game (seem already to be enabled?!!) but the previous CBA and ShackTac HUD mods are no longer listed!!!......please can someone explain whats happening?
2)Also is there a way to test the mk14 weapons mod is working (do I need to create something in editor - no experience of using this so please guide me) or is there a mission I can run that use the mk14 or m4 weapons?
3)Also in the above advise it tells me to create a folder called @your_mod_folder_name - I presume this means name the folder what you like then extract the zipped mod folder into this and then you drop the whole package into the core ARMA3 folder (so basically you have x2 folders before you reach the actual mod files?(did I understand this right?)